JP6988452B2 - White toner for static charge image development, static charge image developer, toner cartridge, process cartridge, image forming apparatus and image forming method - Google Patents

Description

The present invention relates to a white toner for static charge image development, an electrostatic charge image developer, a toner cartridge, a process cartridge, an image forming apparatus, and an image forming method.

Conventionally, as a white toner used for image formation in an electrophotographic method, a white toner containing a binder resin and a white pigment is known. Patent Document 1 discloses a white toner having a white portion as a core and a transparent portion on the outside. Patent Document 2 discloses a white toner containing titanium oxide having an average particle size of 0.02 μm to 0.35 μm.

When a colored image is directly formed on a colored recording medium or a transparent recording medium, the color reproducibility of the colored image may not be good. Therefore, for the purpose of improving the color reproducibility of a colored image, a white image (generally a white image having a density of 100%) is used as a concealing layer that hides the color of the colored recording medium or suppresses the transparency of the transparent recording medium. , So-called white solid image) may be formed. The concealment property of a white image is exhibited by reflecting the light incident on the white image without transmitting it. Therefore, as a measure for obtaining a white image having excellent concealing property, a white pigment having a high refractive index is used, a white pigment having a primary particle diameter of about half of the wavelength of incident light is used, and a white pigment in a white image is used. It has been proposed to increase the amount of white pigment and to thicken the white image.

Japanese Unexamined Patent Publication No. 2002-108021 Japanese Unexamined Patent Publication No. 01-105961

A recording medium on which an image is formed (eg, a resin film) may be used as a package or label for the article, in which case the recording medium on which the image is formed will be curved along the shape of the article. If the recording medium on which the white image and the colored image, which are the concealing layers, are laminated is curved, the color reproducibility of the colored image may be deteriorated. It is presumed that this phenomenon occurs when light is incident on the white image from various directions in the curved state, and therefore the amount of light transmitted without being reflected increases. This phenomenon tends to be noticeable when the recording medium on which the image is formed is exposed to mechanical stress, and the thicker the white image or the larger the amount of white pigment in the white image. (That is, the less the binder resin is, the more likely it is to occur). From this, the adhesion between the colored image and the white image is reduced, and a gap is generated between the colored image and the white image, which affects the curved state and the color reproducibility of the colored image is lowered. It is also speculated that there is.

This disclosure has been made under the above circumstances.
The present disclosure provides a white toner for static charge image development capable of forming a white image that suppresses a decrease in color reproducibility of a colored image that occurs when a recording medium in which a white image and a colored image are laminated is curved. That is the issue.

Specific means for solving the above-mentioned problems include the following aspects.

The invention according to <1 > is
Contains white toner particles containing a binder resin and a white pigment,
In the circularity distribution of the white pigment obtained by observing the cross section of the white toner particles, the circularity having a cumulative 10% from the smaller side is C10, and the circularity having a cumulative 50% is C50. And a white toner for static charge image development that satisfies the formula (2).
Equation (1): 0.900 ≤ C50 ≤ 1.000
Equation (2): 1.00 ≤ C50 / C10 ≤ 1.13

The invention according to <2 > is
The white toner for static charge image development according to < 1 > , wherein the C50 / C10 satisfies the following formula (2').
Equation (2'): 1.00 <C50 / C10≤1.08

The invention according to <3 > is
In the cross-sectional observation of the white toner particles, when the Voronoi division is performed with the center of gravity of the white pigment as the base point, the average value of the areas of the Voronoi polygon is Sa (μm ² ), and the standard deviation is Ssd (μm ² ). , The white toner for static charge image development according to < 1 > or < 2 > , which satisfies the following formulas (3) and (4).
Equation (3): 0.150 ≤ Sa ≤ 0.350
Equation (4): SSD ≤ 0.250

The invention according to <4 > is
The white toner for static charge image development according to < 3 > , wherein the Sa satisfies the following formula (3').
Equation (3'): 0.180 ≤ Sa ≤ 0.300

The invention according to <5 > is
When the mode of the distribution of the uneven distribution of the white pigment represented by the following formula (A) is Pm and the skewness is Psk, the following formulas (5) and (6) are satisfied, < 1 > ~. The white toner for static charge image development according to any one of <4 >.
Equation (A): Uneven distribution = 2d / D
Equation (5): 0.78 ≤ Pm ≤ 0.98
Equation (6): -1.10 ≤ Psk ≤ -0.60
In the formula (A), D is the equivalent circle diameter (μm) of the white toner particles obtained in the cross-sectional observation of the white toner particles, and d is the white pigment from the center of gravity of the white toner particles obtained in the cross-sectional observation of the white toner particles. The distance to the center of gravity (μm).

The invention according to <6 > is
The white toner for static charge image development according to < 5 > , wherein the Pm satisfies the following formula (5').
Equation (5'): 0.82 ≤ Pm ≤ 0.96

The invention according to <7 > is
The white toner for static charge image development according to < 5 > or < 6 > , wherein the Psk satisfies the following formula (6').
Equation (6'): −0.90 ≦ Psk ≦ −0.60

The invention according to <8 > is
The white toner for static charge image development according to any one of < 1 > to < 6 > , wherein the BET specific surface area of the white pigment is 6.5 m ² / g or more and 8.5 m ² / g or less.

The invention according to <9 > is
A static charge image developer containing the white toner for static charge image development according to any one of < 1 > to < 8 >.

The invention according to <10 > is
The white toner for static charge image development according to any one of <1 > to < 8 > is accommodated, and the white toner is accommodated.
A toner cartridge that is attached to and detached from the image forming device.

The invention according to <11 > is
A developing means for accommodating the electrostatic charge image developer according to < 9 > and developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer is provided.
A process cartridge that is attached to and detached from the image forming device.

The invention according to <12 > is
Image holder and
A charging means for charging the surface of the image holder, and
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image holder, and
A developing means for accommodating the static charge image developer according to < 9 > and developing the static charge image formed on the surface of the image holder as a toner image by the static charge image developer.
A transfer means for transferring a toner image formed on the surface of the image holder to the surface of a recording medium,
A fixing means for fixing the toner image transferred to the surface of the recording medium, and
An image forming apparatus.

The invention according to <13 > is
The charging process that charges the surface of the image holder,
A static charge image forming step of forming a static charge image on the surface of the charged image holder, and
A developing step of developing an electrostatic charge image formed on the surface of the image holder as a toner image by using the electrostatic charge image developer according to < 9 >.
A transfer step of transferring a toner image formed on the surface of the image holder to the surface of a recording medium,
A fixing step of fixing the toner image transferred to the surface of the recording medium, and
Image forming method having.

According to the invention according to < 1 > or < 2 > , the white image and the colored image are laminated as compared with the case where C50 is less than 0.900 or C50 / C10 is more than 1.13. Provided is a white toner for static charge image development capable of forming a white image that suppresses a decrease in color reproducibility of a colored image that occurs when the recording medium is curved.
According <3> or to the invention according to <4>, as compared with the case where the average value is 0.150 ² less than or 0.350Myuemu ² or greater than the standard deviation of the area of the Voronoi polygon is 0.250 ² greater, Provided is a white toner for static charge image development capable of forming a white image that suppresses a decrease in color reproducibility of a colored image that occurs when a recording medium in which a white image and a colored image are laminated is curved.
According to the invention according to < 5 > , < 6 > or < 7 >, when the most frequent value of the distribution of the uneven distribution of the white pigment is less than 0.78 or more than 0.98, or the distortion degree is -1. A white image is formed that suppresses the deterioration of the color reproducibility of the colored image that occurs when the recording medium in which the white image and the colored image are laminated is curved, as compared with the case of less than .10 or more than -0.60. A possible static charge image development white toner is provided.
According to the invention according to < 8 > , a recording in which a white image and a colored image are laminated as compared with the case where the BET specific surface area of the white pigment is ^{less than 6.5 m 2} / g or more than 8.5 m ^{2 / g.} Provided is a white toner for static charge image development capable of forming a white image that suppresses a decrease in color reproducibility of a colored image that occurs when the medium is curved.

According to the invention according to < 9 > , the recording medium in which the white image and the colored image are laminated is compared with the case where C50 is less than 0.900 or C50 / C10 is more than 1.13. Provided is a static charge image developer containing a white toner for static charge image development capable of forming a white image that suppresses a decrease in color reproducibility of a colored image that occurs when the image is curved.
According to the invention according to < 10 > , the recording medium in which the white image and the colored image are laminated is compared with the case where C50 is less than 0.900 or C50 / C10 is more than 1.13. Provided is a toner cartridge containing a white toner for static charge image development capable of forming a white image that suppresses a decrease in color reproducibility of a colored image that occurs when the image is curved.
According to the invention according to < 11 > , < 12 > or < 13 > , the white image and the colored image are compared with the case where C50 is less than 0.900 or C50 / C10 is more than 1.13. A process cartridge to which a static charge image developer containing a white toner for static charge image development that can form a white image that suppresses the deterioration of color reproducibility of a colored image that occurs when the recording medium laminated with and is curved is applied. , An image forming apparatus or an image forming method is provided.

It is a schematic block diagram which shows an example of the image forming apparatus which concerns on this embodiment. It is a schematic block diagram which shows an example of the process cartridge which concerns on this embodiment.

Hereinafter, embodiments of the invention will be described. These explanations and examples are illustrative of embodiments and do not limit the scope of the invention.

When referring to the amount of each component in the composition in the present disclosure, if a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, the plurality of species present in the composition. It means the total amount of substances.

The numerical range indicated by using "~" in the present disclosure indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.

In the present disclosure, "toner for static charge image development" is also referred to simply as "toner", "white toner for static charge image development" is also referred to simply as "white toner", and "electrostatic image developer" is simply referred to as "developer". Also called.

<White toner for static charge image development>
The white toner according to the present embodiment contains white toner particles containing a binder resin and a white pigment, and the circularity is 10% cumulative from the smaller side in the circularity distribution of the white pigment obtained by observing the cross section of the white toner particles. Is C10, and the circularity with a cumulative total of 50% is C50, the following equations (1) and (2) are satisfied.

Equation (1): 0.900 ≤ C50 ≤ 1.000
Equation (2): 1.00 ≤ C50 / C10 ≤ 1.13

The formula (1) indicates that the circularity of the white pigment contained in the white toner particles is high, and the formula (2) indicates that the circularity distribution of the white pigment contained in the white toner particles is narrow. ..

In the white toner of the present embodiment, the circularity of the white pigment contained in the white toner particles is high (that is, the white pigment has few angles), and the circularity distribution of the white pigment is narrow. This white toner has high isotropic particle shape of the white pigment, and can exhibit a high light scattering rate regardless of the incident direction of light. Therefore, it is presumed that the white image containing the white pigment has excellent concealing property even in a curved state in which light is incident from various directions, and suppresses deterioration of the color reproducibility of the colored image. When C50 is less than 0.900, or when C50 / C10 is more than 1.13, the isotropic property of the particle shape of the white pigment and the light scattering rate are not sufficient, so that the hiding property of the white image is poor. It is presumed that it is not sufficient to suppress the deterioration of the color reproducibility of the colored image in the curved state.

From the above viewpoint, in the present embodiment, C50 related to the circularity of the white pigment is 0.900 or more and 1.000 or less, and C50 / C10 is 1.13 or less. The smaller the C50 / C10, the more preferable it is, ideally 1.00, and practically more than 1.00.
The C50 relating to the circularity of the white pigment is more preferably the formula (1'): 0.925 ≦ C50 ≦ 1.000, and further preferably the formula (1 ″): 0.950 ≦ C50 ≦ 1. C50 / C10 relating to the circularity of the white pigment is more preferably the formula (2'): 1.00 <C50 / C10 ≦ 1.08, and further preferably the formula (2 ″) :. 1.00 <C50 / C10 ≦ 1.05.

Further, according to the white toner of the present embodiment, the deterioration of the color reproducibility of the colored image in the curved state can be suppressed by the above mechanism, so that the white image can be made relatively thick or the white image can be obtained. It is not necessary to increase the amount of white pigment in the medium. Therefore, it is possible to suppress the formation of a gap between the colored image and the white image, and it is presumed that the deterioration of the color reproducibility of the colored image is also suppressed in this respect.

In the formulas (1) and (2) relating to the white pigment in the white toner particles, when the white toner particles are produced by the aggregation and coalescence method, the corners of the white pigment particles are determined by using a dispersion treatment apparatus having excellent crushing power. This can be achieved by preparing a white pigment particle dispersion while taking it.

In the white toner of the present embodiment, in the cross-sectional observation of the white toner particles, the Voronoi division is performed with the center of gravity of the white pigment as the base point, the average value of the area of the Voronoi polygon is Sa (μm ² ), and the standard deviation is Ssd (. When μm ² ), it is preferable to satisfy the following equations (3) and (4).

Equation (3): 0.150 ≤ Sa ≤ 0.350
Equation (4): SSD ≤ 0.250

The numerical ranges of Sa and Ssd indicate that the white pigment is uniformly dispersed in the white toner particles without agglomeration, and the distance between the white pigments is appropriate. A white toner satisfying the formulas (3) and (4) can form a white image that is less likely to transmit light, and is superior in color reproducibility of a colored image in a curved state.

The Sa is more preferably the formula (3'): 0.180 ≦ Sa ≦ 0.300, and further preferably the formula (3 ″): 0.200 ≦ Sa ≦ 0.270.

The Ssd is more preferably 0.200 or less, still more preferably 0.170 or less. The smaller the Ssd, the more preferable, but in reality, it is 0.100 or more, and generally 0.120 or more.

Further, in the white toner of the present embodiment, when the mode of the distribution of the uneven distribution of the white pigment represented by the following formula (A) is Pm and the skewness is Psk, the following formula (5) and the formula are used. It is preferable to satisfy (6).

Equation (A): Uneven distribution = 2d / D
Equation (5): 0.78 ≤ Pm ≤ 0.98
Equation (6): -1.10 ≤ Psk ≤ -0.60
In the formula (A), D is the equivalent circle diameter (μm) of the white toner particles obtained in the cross-sectional observation of the white toner particles, and d is the white pigment from the center of gravity of the white toner particles obtained in the cross-sectional observation of the white toner particles. The distance to the center of gravity (μm).

The numerical ranges of Pm and Psk indicate that the white pigment is uniformly dispersed from the center of the white toner particles to the vicinity of the surface with little bias. A white toner satisfying the formulas (5) and (6) can form a white image that is less likely to transmit light, and is superior in color reproducibility of a colored image in a curved state.

The Pm is more preferably the formula (5'): 0.82 ≦ Pm ≦ 0.96, and further preferably the formula (5 ″): 0.85 ≦ Pm ≦ 0.95.

The Psk is more preferably of the formula (6'): −0.90 ≦ Psk ≦ −0.60, and more preferably of the formula (6 ″): −0.80 ≦ Psk ≦ −0.75. be.

The numerical ranges of Sa and Ssd related to the white pigment in the white toner particles, and the numerical ranges of Pm and Psk are the BET ratios of the white pigment used as a material when the toner particles are produced by the aggregation and coalescence method. This can be achieved by setting the surface area to an appropriate range and uniformly dispersing the particles in the solvent.

[Cross-section observation of white toner particles]
Here, a method of observing a cross section of white toner particles in the present embodiment and a method of obtaining each physical property based on the method will be described.

-Preparation of observation sample and extraction of observation cross section-
Toner particles (which may have an external additive attached) are embedded with a bisphenol A type liquid epoxy resin and a curing agent to prepare a sample for cutting. Using a cutting machine equipped with a diamond knife (for example, LEICA Ultra Microtome, manufactured by Hitachi High-Technologies Corporation), the cutting sample is cut at −100 ° C. to prepare an observation sample. If necessary, the observation sample is left in a desiccator under a ruthenium tetroxide atmosphere for staining.
The observation sample thus obtained is observed with a scanning transmission electron microscope (STEM), and a STEM image is recorded at a magnification that allows the cross section of one toner particle to be in the field of view. The recorded STEM image was analyzed using image analysis software (WinROOF2015, Mitani Shoji Co., Ltd.) under the condition of 0.010000 μm / pixel, and the difference in brightness between the epoxy resin for embedding and the binder resin of the toner particles. (Contrast) determines the cross-sectional shape of the toner particles.

-Circular distribution of white pigment-
In the STEM image, the white pigment looks black due to the difference in brightness (contrast) between the binder resin, the mold release agent, and the like, so the black particles in the cross section of the toner particles are the white pigment. Using the above image analysis software, image analysis is performed under the condition of 0.010000 μm / circle to determine the cross-sectional shape of the white pigment (black particles), and all the white pigments (all white pigments existing in the area of one toner particle) ( For black particles), the area of the particle image and the peripheral length of the particle image are obtained, and the circularity (= 4π × (area of the particle image) ÷ (peripheral length of the particle image) ² ) is calculated. Further, the above is performed for at least 200 toner particles, and the data section is statistically analyzed in increments of 0.001 to obtain a circularity distribution. In this circularity distribution, the circularity having a cumulative total of 10% from the small side is defined as C10, and the circularity having a cumulative total of 50% from the small side is defined as C50.

-Average diameter of white pigment-
The equivalent circle diameter (= 2√ (area of particle image / π)) is calculated from the area of the particle image used to obtain the circularity distribution of the white pigment and averaged. The measurement point (that is, the number of samples) is It is the same as the circularity distribution.

-Center of gravity of white pigment-
When the number of pixels in the white pigment region is n and the xy coordinates of each pixel are _xi , y _i (i = 1, 2, ..., N), the x coordinate of the center of gravity = ( _{total of x i} ) / n , The y coordinate of the center of gravity = ( _{total of y i} ) / n.

-Circular equivalent diameter D of toner particles-
The projected area of the toner particles is obtained based on the cross-sectional shape, and the equivalent circle diameter (= 2√ (area / π)) is calculated from this area and used as the equivalent circle diameter D of the toner particles.

-Center of gravity of toner particles-
When the number of pixels in the area of the toner particles is n and the xy coordinates of each pixel are x _i , y _i (i = 1, 2, ..., N), the x coordinate of the center of gravity = ( _{total of x i} ) / n , The y coordinate of the center of gravity = ( _{total of y i} ) / n.

-Distance from the center of gravity of the toner particles to the center of gravity of the white pigment d-
The distance d is calculated from the xy coordinates of the center of gravity of the toner particles and the xy coordinates of the center of gravity of the white pigment.

-Average value Sa and standard deviation Ssd of the area of the Voronoi polygon-
Voronoi polygon division with the center of gravity of all white pigments existing in the region of one toner particle as the population point (a vertical bisector is drawn on the straight line connecting the adjacent population points, and the region closest to each population point. And measure the area of all the Voronoi polygons formed. If the observation field contains toner particles that are not the observation target, or if there is a black image area that causes noise in the vicinity of the toner particles that are the observation target, the observation target is used when performing image analysis. It is specified to exclude the area other than the toner particles of.
Further, the above is performed for at least 200 toner particles, and the average value Sa and the standard deviation Ssd of the area of the Voronoi polygon are calculated.

-The degree of uneven distribution of the white pigment represented by the formula (A), the distribution of the degree of uneven distribution, the mode Pm and the skewness Psk-
From the circle equivalent diameter D and the distance d, the uneven distribution degree of the white pigment = 2d / D is calculated. The degree of uneven distribution of the white pigment is calculated for all the white pigments existing in the region of one toner particle. Further, the above is performed for at least 200 toner particles, and the data section is statistically analyzed in increments of 0.01 to obtain a distribution of uneven distribution. The mode Pm is a value at which the frequency peaks in the histogram depicting the distribution of the uneven distribution. The skewness Psk is calculated by the following formula.

式中、Ｓｋは歪度、ｎは標本数、ｘ_ｉ（ｉ＝１，２，…，ｎ）は各標本の偏在度、上方にバーを付したｘは全標本の偏在度の平均値、ｓは全標本の偏在度の標準偏差である。

In the equation, Sk is the skewness, n is the number of samples, x _i (i = 1, 2, ..., N) is the uneven distribution of each sample, and x with a bar above is the average value of the uneven distribution of all samples. s is the standard deviation of the skewness of all samples.

Hereinafter, the composition of the toner according to the present embodiment will be described in detail.

[White toner particles]
The white toner particles contain at least a binder resin and a white pigment, and if necessary, a mold release agent and other additives.

-Bound resin-
Examples of the binder resin include styrenes (eg, styrene, parachlorostyrene, α-methylstyrene, etc.), (meth) acrylic acid esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, etc.). N-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (eg, 2-ethylhexyl methacrylate) , Acrylonitrile, methacrylnitrile, etc.), Vinyl ethers (eg, vinyl methyl ether, vinyl isobutyl ether, etc.), Vinyl ketones (eg, vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (eg, ethylene) , Styrene, butadiene, etc.), or a vinyl-based resin composed of a copolymer obtained by combining two or more of these monomers.
Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosins, mixtures of these with the vinyl resins, or these. Examples thereof include a graft polymer obtained by polymerizing a vinyl-based monomer in the coexistence.
These binder resins may be used alone or in combination of two or more.

As the binder resin, polyester resin is suitable. Examples of the polyester resin include a condensed polymer of a polyvalent carboxylic acid and a polyhydric alcohol.

Examples of the polyvalent carboxylic acid include aliphatic dicarboxylic acids (eg, oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid and the like. ), Alicyclic dicarboxylic acid (eg, cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acid (eg, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), anhydrides thereof, or lower grades thereof (eg, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.). Examples thereof include (1 or more and 5 or less carbon atoms) alkyl esters. Among these, as the polyvalent carboxylic acid, for example, an aromatic dicarboxylic acid is preferable.
As the polyvalent carboxylic acid, a trivalent or higher carboxylic acid having a crosslinked structure or a branched structure may be used in combination with the dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower (for example, 1 to 5 carbon atoms) alkyl esters thereof.
One type of polyvalent carboxylic acid may be used alone, or two or more types may be used in combination.

Examples of the polyhydric alcohol include aliphatic diols (eg, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.) and alicyclic diols (eg, cyclohexanediol, cyclohexanedi). Examples thereof include methanol, hydrogenated bisphenol A, etc.) and aromatic diols (eg, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc.). Among these, as the polyhydric alcohol, for example, aromatic diols and alicyclic diols are preferable, and aromatic diols are more preferable.
As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked structure or a branched structure may be used in combination with the diol. Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolpropane, and pentaerythritol.
One type of polyhydric alcohol may be used alone, or two or more types may be used in combination.

The glass transition temperature (Tg) of the polyester resin is preferably 50 ° C. or higher and 80 ° C. or lower, and more preferably 50 ° C. or higher and 65 ° C. or lower. The glass transition temperature of the polyester resin is obtained from the DSC curve obtained by differential scanning calorimetry (DSC), and more specifically described in JIS K7121-1987 "Method for measuring the transition temperature of plastics". It is obtained by the "extra glass transition start temperature" of.

The weight average molecular weight (Mw) of the polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the polyester resin is preferably 2000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.
The weight average molecular weight and the number average molecular weight of the polyester resin are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is carried out by using Tosoh's GPC / HLC-8120GPC as a measuring device, using Tosoh's column / TSKgel SuperHM-M (15 cm), and using a THF solvent. The weight average molecular weight and the number average molecular weight are calculated from this measurement result using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample.

The polyester resin is obtained by a known production method. Specifically, for example, it can be obtained by a method in which the polymerization temperature is set to 180 ° C. or higher and 230 ° C. or lower, the pressure inside the reaction system is reduced as necessary, and the reaction is carried out while removing water and alcohol generated during condensation.
When the raw material monomer is not dissolved or compatible at the reaction temperature, a solvent having a high boiling point may be added as a dissolution aid to dissolve the raw material. In this case, the polycondensation reaction is carried out while distilling off the dissolution aid. If there is a monomer with poor compatibility, it is advisable to condense the monomer with poor compatibility with the monomer and the acid or alcohol to be polycondensed in advance, and then polycondensate with the main component. ..

The content of the binder resin is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and further preferably 60% by mass or more and 85% by mass or less with respect to the entire toner particles.

-White pigment-
Examples of the white pigment include inorganic oxide particles, and specific examples thereof include titanium oxide (TiO ₂ ), silicon dioxide (SiO ₂ ), and alumina (Al ₂ O ₃ ). These white pigments may be used alone or in combination of two or more.

As the white pigment, titanium oxide is preferable from the viewpoint of excellent hiding power. The crystal structure of titanium oxide may be any of anatase type, rutile type and brookite type.

As the white pigment, a surface-treated white pigment may be used or may be used in combination with a dispersant, if necessary.

The average diameter of the white pigment is preferably 150 nm or more and 400 nm or less, more preferably 180 nm or more and 380 nm or less, and further preferably 200 nm or more and 350 nm or less from the viewpoint of excellent hiding power. As described above, the average diameter of the white pigment is determined by observing the cross section of the white toner particles.

BET specific surface area of the white pigment, from the viewpoint of excellent hiding property of the white image, preferably 6.5m ² / g or more 8.5 m ² / g or less, 6.8 m ² / g or more 8.2 m ² / g or less More preferably, it is more preferably 7.0 m ² / g or more and 8.0 m ² / g or less.

The BET specific surface area of the white pigment is determined by the following measuring method.
When the toner particles are externally added with an external additive, the toner particles are suspended in water to which a surfactant is added, ultrasonic waves are applied, and then centrifugation is performed to separate the external additive and the toner particles. Then, the toner particles are suspended in a solvent (for example, tetrahydrofuran) to dissolve the binder resin in the solvent. Then, it is filtered to separate into solid and liquid, and the solid is thoroughly washed with water and then dried to obtain a powder (that is, a white pigment). Using this powder as a sample, the BET specific surface area is measured by the BET multipoint method using nitrogen gas.

The following can be considered as the reason why the white image is excellent in concealing property when the BET specific surface area of the white pigment is in the above range.
When the BET specific surface area of the white pigment used as the material of the toner particles is within an appropriate range, the toner particles are easily compatible with the surfactant when the toner particles are produced by the aggregation and coalescence method, and as a result, the toner particles are easily dispersed in the solvent. It is presumed that the particles are evenly dispersed in the white image to improve the concealment of the white image. When the white pigment used as the material is crushed in the step of preparing the white pigment particle dispersion liquid, it is preferable that the white pigment exhibits a BET specific surface area in the above range in a state of being contained in the toner particles.

The content of the white pigment is preferably 15% by mass or more and 45% by mass or less, and more preferably 20% by mass or more and 40% by mass or less with respect to the entire toner particles.

-Release agent-
Examples of the release agent include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester waxes such as fatty acid esters and montanic acid esters. ; And so on. The release agent is not limited to this.

The melting temperature of the release agent is preferably 50 ° C. or higher and 110 ° C. or lower, and more preferably 60 ° C. or higher and 100 ° C. or lower. The melting temperature of the release agent is determined by the "melting peak temperature" described in the method for determining the melting temperature of JIS K7121-1987 "Method for measuring the transition temperature of plastics" from the DSC curve obtained by differential scanning calorimetry (DSC). demand.

The content of the release agent is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to the entire toner particles.

-Other additives-
Examples of other additives include known additives such as magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as an internal additive.

[Characteristics of toner particles]
The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure composed of a core portion (core particles) and a coating layer (shell layer) covering the core portion. You may. The toner particles having a core-shell structure are composed of, for example, a core portion containing a binder resin, a colorant and a mold release agent, if necessary, and a coating layer containing the binder resin.

The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 9 μm or less.

The volume average particle size of the toner particles is measured using Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolytic solution is measured using ISOTON-II (manufactured by Beckman Coulter). At the time of measurement, 0.5 mg or more and 50 mg or less of the measurement sample is added to 2 ml of a 5% by mass aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate), and this is added to 100 ml or more and 150 ml or less of the electrolytic solution. The electrolytic solution in which the sample is suspended is dispersed for 1 minute with an ultrasonic disperser, and the particle size of particles in the range of 2 μm or more and 60 μm or less is measured using an aperture with an aperture diameter of 100 μm using a Coulter Multisizer II. .. The number of particles to be sampled is 50,000. In the volume-based particle size distribution of the measured particle size, the particle size cumulatively 50% from the small diameter side is defined as the volume average particle size D50v.

The average circularity of the toner particles is preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less.

The average circularity of the toner particles is obtained by (perimeter equivalent to a circle) / (perimeter) [(perimeter of a circle having the same projected area as the particle image) / (perimeter of the projected image of particles)]. Specifically, it is a value measured by the following method.
First, a flow-type particle image analyzer (Sysmex) that captures a particle image as a still image by sucking and collecting toner particles to be measured, forming a flat flow, and instantly emitting strobe light, and analyzing the particle image. Obtained by FPIA-3000) manufactured by the company. The number of samplings for obtaining the average circularity is set to 3500.
When the toner has an external additive, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additive has been removed.

[External agent]
Examples of the external additive include inorganic particles. As the inorganic particles, SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, CaO, K ₂ O, Na ₂ O, ZrO ₂ , CaO. _{SiO 2, K 2 O · (} TiO 2) n, Al 2 O 3 · 2SiO 2, CaCO 3, MgCO 3, BaSO 4, MgSO 4 , etc. particles.

The surface of the inorganic particles as an external additive should be hydrophobized. The hydrophobizing treatment is performed, for example, by immersing the inorganic particles in the hydrophobizing agent. The hydrophobizing agent is not particularly limited, and examples thereof include a silane-based coupling agent, a silicone oil, a titanate-based coupling agent, and an aluminum-based coupling agent. These may be used alone or in combination of two or more. The amount of the hydrophobizing agent is usually 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

Examples of the external additive include resin particles (resin particles such as polystyrene, polymethylmethacrylate, and melamine resin), cleaning active agents (for example, metal salts of higher fatty acids typified by zinc stearate, particles of fluoropolymer). And so on.

As the external additive in the present embodiment, inorganic oxide particles are preferable, and specifically, particles of titanium oxide (TiO ₂ ), silicon dioxide (SiO ₂ ), or alumina (Al ₂ O ₃ ) are preferable. ..

The inorganic oxide particles as an external additive are preferably spindle-shaped in shape from the viewpoint of being difficult to be embedded in toner particles, and the value obtained by dividing the major axis by the minor axis (major axis / minor axis) is 2.5 or more. It is preferably 0 or less, more preferably 3.0 or more and 6.5 or less, and further preferably 3.5 or more and 6.0 or less.

The major axis / minor axis values of the spindle-shaped inorganic oxide particles are obtained by the following measuring method.
The toner to which the inorganic oxide particles are added is observed with a scanning electron microscope (SEM), and at least 200 particles that appear to be spindle-shaped among the particles adhering to the periphery of the toner particles are extracted. Then, the longest straight line drawn at any two points on the contour line of the spindle-shaped particles is defined as the major axis, and the length of the major axis is defined as the major axis. Further, the straight line drawn inside the contour line of the spindle-shaped particles, which is the longest straight line perpendicular to the long axis, is defined as the minor axis, and the length of the minor axis is defined as the minor axis. The major axis, minor axis and major axis / minor axis are obtained for each spindle-shaped particle, and at least 200 values are averaged.

The amount of the external additive added is preferably 1 part by mass or more and 6 parts by mass or less, and more preferably 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the toner particles.

[Toner manufacturing method]
Next, a method for manufacturing the toner according to the present embodiment will be described.
The toner according to the present embodiment can be obtained by externally adding an externalizing agent to the toner particles after producing the toner particles.

The toner particles may be produced by any of a dry production method (for example, a kneading and pulverizing method, etc.) and a wet production method (for example, an agglomeration coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). There are no particular restrictions on these manufacturing methods, and known manufacturing methods are adopted. Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

Specifically, for example, when the toner particles are produced by the aggregation and coalescence method,
A step of preparing a resin particle dispersion liquid in which resin particles to be a binding resin are dispersed (resin particle dispersion liquid preparation step) and a step in the resin particle dispersion liquid (after mixing other particle dispersion liquids as necessary). (In the dispersion liquid), the step of aggregating the resin particles (other particles if necessary) to form the agglomerated particles (aggregated particle forming step), and the step of heating the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed to agglomerate. Toner particles are manufactured through a step of fusing and coalescing the particles to form toner particles (fusing and coalescing step).

Hereinafter, details of each step of the aggregation and coalescence method will be described. In the following description, a method for obtaining toner particles containing a mold release agent will be described, but the mold release agent is used as needed. Of course, other additives other than the release agent may be used.

-Resin particle dispersion liquid preparation process-
Along with the resin particle dispersion liquid in which the resin particles to be the binding resin are dispersed, the white pigment particle dispersion liquid in which the white pigment is dispersed and the release agent particle dispersion liquid in which the release agent particles are dispersed are prepared.

The resin particle dispersion liquid is prepared, for example, by dispersing the resin particles in a dispersion medium with a surfactant.

Examples of the dispersion medium used for the resin particle dispersion liquid include an aqueous medium.
Examples of the aqueous medium include distilled water, water such as ion-exchanged water, and alcohols. These may be used alone or in combination of two or more.

Examples of the surfactant include anionic surfactants such as sulfate ester salt type, sulfonate type, phosphoric acid ester type and soap type; cationic surfactants such as amine salt type and quaternary ammonium salt type; polyethylene glycol. Non-ionic surfactants such as systems, alkylphenol ethylene oxide adducts, and polyhydric alcohols; and the like. Among these, anionic surfactants and cationic surfactants are particularly mentioned. The nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant.
One type of surfactant may be used alone, or two or more types may be used in combination.

Examples of the method for dispersing the resin particles in the dispersion medium include a general dispersion method using a rotary shear homogenizer, a ball mill having a medium, a sand mill, a dyno mill, or the like. Depending on the type of resin particles, the resin particles may be dispersed in a dispersion medium by a phase inversion emulsification method. In the phase inversion emulsification method, the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, and the organic continuous phase (O phase) is neutralized by adding a base, and then water (W phase). This is a method in which the phase is changed from W / O to O / W by charging the resin, and the resin is dispersed in an aqueous medium in the form of particles.

The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and further preferably 0.1 μm or more and 0.6 μm or less. ..
The volume average particle size of the resin particles is the volume with respect to the divided particle size range (channel) using the particle size distribution obtained by the measurement of the laser diffraction type particle size distribution measuring device (for example, manufactured by Horiba Seisakusho, LA-700). The cumulative distribution is drawn from the small particle size side, and the particle size having a volume of 50% with respect to all the particles is defined as the volume average particle size D50v. The volume average particle size of the particles in the other dispersions is measured in the same manner.

The content of the resin particles contained in the resin particle dispersion is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

A release agent particle dispersion is also prepared in the same manner as the resin particle dispersion. That is, the dispersion medium, the dispersion method, the volume average particle size of the particles, and the content of the particles in the resin particle dispersion are the same in the release agent particle dispersion.

A white pigment particle dispersion is also prepared in the same manner as the resin particle dispersion. In the preparation of the white pigment particle dispersion, it is preferable to prepare the white pigment particle dispersion while removing the corners of the white pigment particles using a dispersion treatment apparatus having excellent crushing power.

The volume average particle size (measured by a laser diffraction type particle size distribution measuring device) of the white pigment particles in the white pigment particle dispersion is preferably 200 nm or more and 900 nm or less, more preferably 250 nm or more and 800 nm or less, and 300 nm or more and 700 nm or less. More preferred.
The content of the white pigment particles contained in the white pigment particle dispersion is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

-Agglomerated particle formation process-
Next, the resin particle dispersion liquid, the white pigment particle dispersion liquid, and the release agent particle dispersion liquid are mixed. Then, in the mixed dispersion, the resin particles, the white pigment particles, and the release agent particles are heteroaggregated to form aggregated particles having a diameter close to the diameter of the target toner particles.

Specifically, for example, a flocculant is added to the mixed dispersion, the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 or more and 5 or less), a dispersion stabilizer is added as necessary, and then the resin particles. (Specifically, for example, the glass transition temperature of the resin particles is -30 ° C or higher and the glass transition temperature is -10 ° C or lower), and the particles dispersed in the mixed dispersion are aggregated. , Form agglomerated particles.
In the agglomerated particle forming step, for example, the mixed dispersion is stirred with a rotary shear homogenizer, and the flocculant is added at room temperature (for example, 25 ° C.) to adjust the pH of the mixed dispersion to acidic (for example, pH 2 or more and 5 or less). Then, if necessary, heating may be performed after adding the dispersion stabilizer.

Examples of the flocculant include a surfactant contained in the mixed dispersion and a surfactant having the opposite polarity, an inorganic metal salt, and a metal complex having a valence of 2 or more. When a metal complex is used as the flocculant, the amount of the flocculant used is reduced and the charging characteristics are improved.
Along with the flocculant, an additive that forms a complex or similar bond with the metal ion of the flocculant may be used. As this additive, a chelating agent is preferably used.

Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride and aluminum sulfate; and inorganic metal salts such as polyaluminum chloride, polyaluminum hydroxide and calcium polysulfide. Polymers; and the like.
As the chelating agent, a water-soluble chelating agent may be used. Examples of the chelating agent include oxycarboxylic acids such as tartrate acid, citric acid and gluconic acid; aminocarboxylic acids such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA); ..
The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass with respect to 100 parts by mass of the resin particles.

-Fusion / unification process-
Next, the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed is heated to, for example, a temperature equal to or higher than the glass transition temperature of the resin particles (for example, a temperature 10 ° C. to 30 ° C. higher than the glass transition temperature of the resin particles) to obtain the agglomerated particles. Are fused and united to form toner particles.

Toner particles are obtained through the above steps.
After obtaining the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed, the agglomerated particle dispersion liquid and the resin particle dispersion liquid in which the resin particles are dispersed are further mixed, and the resin particles are further adhered to the surface of the agglomerated particles. The step of forming the second agglomerated particles and the second agglomerated particle dispersion liquid in which the second agglomerated particles are dispersed are heated to fuse and unite the second agglomerated particles to form a core. -The toner particles may be manufactured through the steps of forming the toner particles having a shell structure.

After the completion of the fusion / coalescence step, the toner particles formed in the solution are subjected to a known cleaning step, solid-liquid separation step, and drying step to obtain a dried toner particle. In the cleaning step, from the viewpoint of chargeability, it is preferable to sufficiently perform replacement cleaning with ion-exchanged water. In the solid-liquid separation step, suction filtration, pressure filtration and the like may be performed from the viewpoint of productivity. From the viewpoint of productivity, the drying step may be freeze-dried, air-flow-dried, fluid-dried, vibrating fluid-dried or the like.

The toner according to the present embodiment is produced, for example, by adding an external additive to the toner particles in a dry state and mixing them. The mixing may be performed by, for example, a V blender, a Henschel mixer, a Ladyge mixer or the like. Further, if necessary, the coarse particles of the toner may be removed by using a vibration master, a wind master, or the like.

<Static charge image developer>
The electrostatic charge image developer according to the present embodiment contains at least the white toner according to the present embodiment. The electrostatic charge image developer according to the present embodiment may be a one-component developer containing only the white toner according to the present embodiment, or may be a two-component developer in which the toner and the carrier are mixed. ..

The carrier is not particularly limited, and examples thereof include known carriers. As the carrier, for example, a coating carrier in which the surface of a core material made of magnetic powder is coated with a resin; a magnetic powder dispersion type carrier in which magnetic powder is dispersed in a matrix resin; a porous magnetic powder is impregnated with a resin. Examples thereof include a resin-impregnated carrier. The magnetic powder dispersion type carrier and the resin impregnated type carrier may be carriers in which the constituent particles of the carrier are used as a core material and the surface thereof is coated with a resin.

Examples of the magnetic powder include magnetic metals such as iron, nickel and cobalt; magnetic oxides such as ferrite and magnetite; and the like.

Examples of the coating resin and matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, and styrene-acrylic acid. Examples thereof include an ester copolymer, a straight silicone resin containing an organosiloxane bond or a modified product thereof, a fluororesin, a polyester, a polycarbonate, a phenol resin, an epoxy resin and the like. The coating resin and the matrix resin may contain additives such as conductive particles. Examples of the conductive particles include metals such as gold, silver and copper; particles such as carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate and potassium titanate.

Examples of coating the surface of the core material with a resin include a method of coating with a coating resin and a coating layer forming solution in which various additives (used as necessary) are dissolved in an appropriate solvent. The solvent is not particularly limited, and may be selected in consideration of the type of resin to be used, coating suitability, and the like. Specific resin coating methods include a dipping method in which the core material is immersed in a coating layer forming solution; a spray method in which the coating layer forming solution is sprayed onto the core material surface; and the core material is suspended by flowing air. A fluid bed method in which a solution for forming a coating layer is sprayed; a kneader coater method in which a core material of a carrier and a solution for forming a coating layer are mixed in a kneader coater and then the solvent is removed; and the like can be mentioned.

The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner: carrier = 1: 100 to 30: 100, and more preferably 3: 100 to 20: 100.

<Image forming device, image forming method>
An image forming apparatus and an image forming method according to the present embodiment will be described.
The image forming apparatus according to the present embodiment includes an image holder, a charging means for charging the surface of the image holder, a static charge image forming means for forming an electrostatic charge image on the surface of the charged image holder, and an electrostatic charge. A developing means that accommodates an image developer and develops an electrostatic charge image formed on the surface of an image holder as a toner image by the static charge image developer, and a recording medium that records a toner image formed on the surface of the image holder. It is provided with a transfer means for transferring to the surface of the recording medium and a fixing means for fixing the toner image transferred to the surface of the recording medium. Then, as the static charge image developer, the static charge image developer according to the present embodiment is applied.

In the image forming apparatus according to the present embodiment, a charging step of charging the surface of the image holder, a static charge image forming step of forming an electrostatic charge image on the surface of the charged image holder, and an electrostatic charge according to the present embodiment. A development step of developing an electrostatic charge image formed on the surface of an image holder as a toner image with an image developer, and a transfer step of transferring a toner image formed on the surface of the image holder to the surface of a recording medium. An image forming method (image forming method according to the present embodiment) having a fixing step of fixing a toner image transferred to the surface of a recording medium is carried out.

The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers the toner image formed on the surface of the image holder to the recording medium; the toner image formed on the surface of the image holder is transferred to the intermediate transfer body. An intermediate transfer type device that first transfers the toner image to the surface and then secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium; the surface of the image holder after the transfer of the toner image and before charging is cleaned. A known image forming apparatus such as a device provided with a cleaning means; a device provided with a static elimination means for irradiating the surface of an image holder with static elimination light after transfer of a toner image and before charging; is applied.

When the image forming apparatus according to the present embodiment is an intermediate transfer type apparatus, the transfer means is, for example, an intermediate transfer body in which a toner image is transferred to the surface and an intermediate transfer body in which the toner image formed on the surface of the image holder is transferred. A configuration having a primary transfer means for primary transfer to the surface of the body and a secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium is applied.

In the image forming apparatus according to the present embodiment, for example, the portion including the developing means may have a cartridge structure (process cartridge) attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge containing the electrostatic charge image developer according to the present embodiment and provided with developing means is preferably used.

The image forming apparatus according to the present embodiment may be a tandem type image forming apparatus in which at least one of an image forming unit for forming a white toner image and at least one of an image forming unit for forming a colored toner image are arranged in parallel. , It may be a monochromatic image forming apparatus that forms only a white image. In the latter case, a white image is formed on one recording medium by the image forming apparatus according to the present embodiment, and a colored image is formed by another image forming apparatus.

The recording medium on which the image forming apparatus (image forming method) according to the present embodiment records an image is not particularly limited, and a known recording medium is applied. For example, a resin film or a sheet, paper or the like can be mentioned. Applications of the resin film or sheet include packages, labels, packaging materials, advertising media, transparencies and the like.

The resin film or sheet includes a polyolefin film or sheet such as polyethylene or polypropylene; a polyester film or sheet such as polyethylene terephthalate or polybutylene terephthalate; a polyamide film or sheet such as nylon; a polycarbonate, polystyrene, modified polystyrene, polyvinyl chloride or polyvinyl. Films or sheets of alcohol, polylactic acid and the like; and the like. These films or sheets may be unstretched films or sheets, or uniaxially stretched or biaxially stretched stretched films or sheets. The resin film or sheet may be in the form of either a single layer or a multilayer. The resin film or sheet may be a film having a surface coat layer that assists toner fixing, or a film or sheet that has been subjected to corona treatment, ozone treatment, plasma treatment, frame treatment, glow discharge treatment, or the like.

Examples of the stacking order of the recording medium, the colored image, and the white image (concealing layer) include the following (a), (b), and (c).
Laminating order (a): A transparent recording medium / colored image / white image (concealing layer) from the side closer to the viewer.
Stacking order (b): Colored image / transparent recording medium / white image (concealed layer) from the side closer to the viewer.
Laminating order (c): Colored image / white image (concealing layer) / recording medium (regardless of whether or not it is transparent) from the side closer to the viewer.

Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. In the following description, the main parts shown in the figure will be described, and the description thereof will be omitted.

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment, and is a diagram showing an image forming apparatus of a 5-series tandem system and an intermediate transfer system. The image forming apparatus shown in FIG. 1 (that is, the image forming apparatus in which the image forming units 10W, 10K, 10C, 10M, and 10Y are arranged in the order shown in FIG. 1 and is an intermediate transfer method) is used for a recording medium having transparency. , Used for forming images in the stacking order (a).

The image forming apparatus shown in FIG. 1 outputs an image of each color of white (W), black (K), cyan (C), magenta (M), and yellow (Y) based on color-separated image data. It is equipped with photographic first to fifth image forming units 10W, 10K, 10C, 10M, and 10Y (image forming means). These image forming units (hereinafter, may be simply referred to as “units”) 10W, 10K, 10C, 10M, and 10Y are arranged side by side at a predetermined distance from each other in the horizontal direction. These units 10W, 10K, 10C, 10M, and 10Y may be process cartridges attached to and detached from the image forming apparatus.

Below each unit 10W, 10K, 10C, 10M, and 10Y, an intermediate transfer belt (an example of an intermediate transfer body) 20 extends through each unit. The intermediate transfer belt 20 is provided by being wound around a drive roll 22, a support roll 23, and an opposed roll 24, which are in contact with the inner surface of the intermediate transfer belt 20, and travel in a direction from the first unit 10W to the fifth unit 10Y. It is designed to do. An intermediate transfer body cleaning device 21 is provided on the image holding surface side of the intermediate transfer belt 20 so as to face the drive roll 22.

Each unit 10W, 10K, 10C, 10M, 10Y developing device (an example of developing means) 4W, 4K, 4C, 4M, 4Y are each white in toner cartridges 8W, 8K, 8C, 8M, 8Y. , Black, cyan, magenta, and yellow toners are supplied.

Since the first to fifth units 10W, 10K, 10C, 10M, and 10Y have the same configuration and operation, here, a white image arranged on the upstream side in the traveling direction of the intermediate transfer belt is formed. The first unit 10W to be used will be described as a representative.

The first unit 10W has a photoconductor 1W that acts as an image holder. Around the photoconductor 1W, a charging roll (an example of charging means) 2W that charges the surface of the photoconductor 1W to a predetermined potential, and the charged surface are exposed to a laser beam based on a color-decomposed image signal. An exposure device (an example of a static charge image forming means) 3W for forming an electrostatic charge image, a developing device (an example of a developing means) for developing a static charge image by supplying toner to the static charge image, and a developed toner image. A primary transfer roll (an example of a primary transfer means) 5W to be transferred onto the intermediate transfer belt 20 and a photoconductor cleaning device (an example of a cleaning means) 6W for removing toner remaining on the surface of the photoconductor 1W after the primary transfer are arranged in order. Has been done.

The primary transfer roll 5W is arranged inside the intermediate transfer belt 20 and is provided at a position facing the photoconductor 1W. A bias power supply (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5W, 5K, 5C, 5M, and 5Y of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll by control by a control unit (not shown).

Hereinafter, the operation of forming a white image in the first unit 10W will be described.
First, prior to the operation, the surface of the photoconductor 1W is charged to a potential of −600V to −800V by the charging roll 2W.
The photoconductor 1W is formed by laminating a photosensitive layer on a conductive substrate (for example, a volume resistivity of 1 × 10 ^{-6 Ωcm or less at 20 ° C.).} This photosensitive layer usually has a high resistivity (resistance of a general resin), but has a property that when a laser beam is irradiated, the specific resistance of the portion irradiated with the laser beam changes. Therefore, the surface of the charged photoconductor 1W is irradiated with a laser beam from the exposure apparatus 3W according to image data for white color sent from a control unit (not shown). As a result, an electrostatic charge image of a white image pattern is formed on the surface of the photoconductor 1W.

The static charge image is an image formed on the surface of the photoconductor 1W by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam from the exposure apparatus 3W, and the surface of the photoconductor 1W is charged. It is a so-called negative latent image formed by the flow of the charged charge and the residual charge of the portion not irradiated with the laser beam.
The electrostatic charge image formed on the photoconductor 1W rotates to a predetermined development position as the photoconductor 1W travels. Then, at this developing position, the electrostatic charge image on the photoconductor 1W is developed and visualized as a toner image by the developing device 4W.

In the developing apparatus 4W, for example, a static charge image developing agent containing at least a white toner and a carrier is housed. The white toner is triboelectrically charged by being agitated inside the developing apparatus 4W, and has a charge having the same polarity (negative electrode property) as the charged charge on the photoconductor 1W, and has a developer roll (developer holder). Example) It is held on. Then, as the surface of the photoconductor 1W passes through the developing device 4W, the white toner is electrostatically adhered to the static-free latent image portion on the surface of the photoconductor 1W, and the latent image is developed by the white toner. Toner. The photoconductor 1W on which the white toner image is formed is continuously traveled at a predetermined speed, and the toner image developed on the photoconductor 1W is conveyed to a predetermined primary transfer position.

When the white toner image on the photoconductor 1W is conveyed to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5W, and the electrostatic force from the photoconductor 1W toward the primary transfer roll 5W acts on the toner image to be photosensitive. The toner image on the body 1W is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a polarity (+) opposite to the polarity (−) of the toner, and is controlled to, for example, +10 μA by a control unit (not shown) in the first unit 10W.
On the other hand, the toner remaining on the photoconductor 1W is removed by the photoconductor cleaning device 6W and recovered.

The primary transfer bias applied to the primary transfer rolls 5M, 5C, 5K, and 5W after the second unit 10M is also controlled according to the first unit.
In this way, the intermediate transfer belt 20 on which the white toner image is transferred by the first unit 10W is sequentially conveyed through the second to fifth units 10M, 10C, 10K, and 10W, and the toner images of each color are superimposed. Multiple transcription is performed.

The intermediate transfer belt 20 to which the toner images of five colors are multiplex-transferred through the first to fifth units includes the intermediate transfer belt 20, the opposed roll 24 in contact with the inner surface of the intermediate transfer belt, and the image holding surface of the intermediate transfer belt 20. It leads to a secondary transfer unit composed of a secondary transfer roll (an example of the secondary transfer means) 26 arranged on the side. On the other hand, the recording paper (an example of the recording medium) P is fed to the gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact with each other via the supply mechanism at a predetermined timing, and the secondary transfer bias is set to the facing roll. It is applied to 24. The transfer bias applied at this time has the same polarity (-) as the toner polarity (-), and the electrostatic force from the intermediate transfer belt 20 toward the resin sheet P (an example of the recording medium) acts on the toner image. , The toner image on the intermediate transfer belt 20 is transferred onto the resin sheet P. The secondary transfer bias at this time is determined according to the resistance detected by the resistance detecting means (not shown) for detecting the resistance of the secondary transfer unit, and is voltage controlled.

After that, the resin sheet P is sent to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (an example of the fixing means) 28, the toner image is fixed on the resin sheet P, and the fixing image is formed. ..

The resin sheet P for which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.

<Process cartridge, toner cartridge>
The process cartridge according to this embodiment will be described.
The process cartridge according to the present embodiment contains the electrostatic charge image developer according to the present embodiment, and is a developing means for developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer. It is a process cartridge that is attached to and detached from the image forming apparatus.

The process cartridge according to the present embodiment includes a developing means and, if necessary, at least one selected from other means such as an image holder, a charging means, an electrostatic charge image forming means, and a transfer means. It may be configured.

Hereinafter, an example of the process cartridge according to the present embodiment will be shown, but the present invention is not limited thereto. In the following description, the main parts shown in the figure will be described, and the description thereof will be omitted.

FIG. 2 is a schematic configuration diagram showing a process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 2 is provided around the photoconductor 107 (an example of an image holder) and the periphery of the photoconductor 107 by, for example, a housing 117 provided with a mounting rail 116 and an opening 118 for exposure. The charged roll 108 (an example of the charging means), the developing device 111 (an example of the developing means), and the photoconductor cleaning device 113 (an example of the cleaning means) are integrally combined and held and configured to form a cartridge. There is.
In FIG. 2, 109 is an exposure device (an example of an electrostatic charge image forming means), 112 is a transfer device (an example of a transfer means), 115 is a fixing device (an example of a fixing means), and 300 is a resin sheet (an example of a recording medium). Is shown.

Next, the toner cartridge according to this embodiment will be described.
The toner cartridge according to the present embodiment is a toner cartridge that accommodates the white toner according to the present embodiment and is attached to and detached from the image forming apparatus. The toner cartridge accommodates a replenishing toner to be supplied to the developing means provided in the image forming apparatus.

The image forming apparatus shown in FIG. 1 is an image forming apparatus having a structure in which toner cartridges 8W, 8K, 8C, 8M, and 8Y are attached and detached, and the developing apparatus 4W, 4K, 4C, 4M, and 4Y are for each color. It is connected to the corresponding toner cartridge with a toner supply pipe (not shown). When the amount of toner contained in the toner cartridge is low, the toner cartridge is replaced. An example of the toner cartridge according to the present embodiment is the toner cartridge 8W, which contains the white toner according to the present embodiment. The toner cartridges 8K, 8C, 8M, and 8Y contain black, cyan, magenta, and yellow toners, respectively.

Hereinafter, embodiments of the invention will be described in detail with reference to Examples, but the embodiments of the invention are not limited to these Examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

<Preparation of particle dispersion, etc.>
[Preparation of white pigment particle dispersion liquid (1)]
-Titanium oxide particles (manufactured by Titan Kogyo Co., Ltd., product number KR-380): 100 parts-Anionic surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Neogen R): 10 parts-Ion-exchanged water: 150 parts

The above materials are mixed in an Iboy wide-mouthed bottle 1000 ml (manufactured by AS ONE, polypropylene), 300 parts of zirconia beads having a diameter of 3 mm are added, and the mixture is rotated at 300 rpm for 24 hours using a ball mill turntable (manufactured by Asahi Rika Seisakusho). After removing the beads from the dispersion with a stainless sieve, ion-exchanged water was added to obtain a white pigment particle dispersion (1) having a solid content of 40%. The volume average particle size of the particles in the white pigment particle dispersion liquid (1) measured by the laser diffraction type particle size distribution measuring device was 500 nm.

[Preparation of white pigment particle dispersion liquid (2)]
A white pigment particle dispersion (2) was obtained in the same manner as in the preparation of the white pigment particle dispersion (1) except that the diameter of the zirconia beads was changed to 5 mm.

[Preparation of white pigment particle dispersion liquid (3)]
A white pigment particle dispersion (3) was obtained in the same manner as in the preparation of the white pigment particle dispersion (1) except that the diameter of the zirconia beads was changed to 1 mm.

[Preparation of white pigment particle dispersion liquid (4)]
A white pigment particle dispersion (4) was obtained in the same manner as in the preparation of the white pigment particle dispersion (1) except that the diameter of the zirconia beads was changed to 1 mm and the rotation treatment time was changed to 72 hours.

[Preparation of white pigment particle dispersion liquid (5)]
The white pigment particle dispersion liquid (5) was obtained in the same manner as in the preparation of the white pigment particle dispersion liquid (1) except that the rotation treatment time was changed to 12 hours.

[Preparation of white pigment particle dispersion liquid (6)]
The white pigment particle dispersion liquid (6) was obtained in the same manner as in the preparation of the white pigment particle dispersion liquid (1) except that the rotation treatment time was changed to 8 hours.

[Preparation of white pigment particle dispersion liquid (7)]
A white pigment particle dispersion (7) was obtained in the same manner as in the preparation of the white pigment particle dispersion (1) except that the amount of the anionic surfactant was changed to 15 parts.

[Preparation of white pigment particle dispersion liquid (8)]
A white pigment particle dispersion (8) was obtained in the same manner as in the preparation of the white pigment particle dispersion (1) except that the amount of the anionic surfactant was changed to 5 parts.

[Preparation of white pigment particle dispersion liquid (9)]
-Titanium oxide particles (manufactured by Titan Kogyo Co., Ltd., product number KR-380): 100 parts-Anionic surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Neogen R): 10 parts-Ion-exchanged water: 150 parts

The above materials are mixed and dispersed for about 10 hours using a high-pressure impact disperser Ultimizer (Sugino Machine Limited, HJP30006), ion-exchanged water is added, and a white pigment particle dispersion having a solid content of 40% ( 9) was obtained.

[Preparation of white pigment particle dispersion liquid (10)]
The white pigment particle dispersion (1) was prepared in the same manner as the preparation of the white pigment particle dispersion (1) except that the titanium oxide particles were changed to the product number JR-603 manufactured by TAYCA and the diameter of the zirconia beads was changed to 5 mm. 10) was obtained.

[Preparation of polyester resin particle dispersion liquid (1)]
In a heat-dried two-necked flask, 74 parts of dimethyl adipate, 192 parts of dimethyl terephthalate, 216 parts of bisphenol A ethylene oxide adduct, 38 parts of ethylene glycol, and 0.037 parts of tetrabutoxytitanate as a catalyst were placed in the flask. After introducing nitrogen gas and keeping the atmosphere in an inert atmosphere and raising the temperature while stirring, the polycondensation polymerization reaction was carried out at 160 ° C. for about 7 hours, and then the temperature was gradually reduced to 10 Torr and the temperature was raised to 220 ° C. and held for 4 hours. .. The polyester resin was synthesized by returning to normal pressure (atmospheric pressure, the same applies hereinafter), adding 9 parts of trimellitic anhydride, gradually reducing the pressure to 10 Torr again, and holding for 1 hour. This polyester resin had a glass transition temperature of 60 ° C., a weight average molecular weight of 12,000, and an acid value of 25.0 mgKOH / g.

115 parts of polyester resin, 180 parts of ion-exchanged water, and 5 parts of anionic surfactant (Neogen R, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are mixed and heated to 120 ° C., and then a homogenizer (manufactured by IKA, Ultrata). After sufficient dispersion with Lux T50), dispersion treatment is performed with a pressure discharge homogenizer (Gorin homogenizer manufactured by Gorin) for 1 hour, ion-exchanged water is added, and a polyester resin particle dispersion liquid (1) having a solid content of 20% is added. Got The volume average particle size of the resin particles in the polyester resin particle dispersion liquid (1) was 130 nm.

[Preparation of release agent particle dispersion liquid (1)]
-Paraffin wax (HNP9 manufactured by Nippon Seiro Co., Ltd., melting temperature 72 ° C): 90 parts-Anionic surfactant (Neogen R, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.): 3.6 parts-Ion-exchanged water: 360 parts

After mixing the above materials and heating to 100 ° C. to dissolve the wax, a pressure discharge homogenizer (Gorin homogenizer manufactured by Gorin) is used for dispersion treatment at a dispersion pressure of 5 MPa for 2 hours, and then a dispersion pressure of 40 MPa for 3 hours. The dispersion treatment was carried out to obtain a mold release agent particle dispersion liquid (1) having a solid content of 20%. The volume average particle size of the particles in the release agent particle dispersion liquid (1) was 230 nm.

[Creation of carrier]
-Ferrite particles (volume average particle size 35 μm): 100 parts-Toluene: 14 parts-styrene / methyl methacrylate copolymer (copolymerization ratio 15/85): 3 parts-Carbon black (Cabot, Regal330): 0.2 Department

The above materials excluding ferrite particles were dispersed in a sand mill to prepare a dispersion, and the dispersion was placed in a vacuum degassed kneader together with the ferrite particles and dried under reduced pressure while stirring to obtain carriers.

<Manufacturing of white toner and white developer>
[Example 1]
-Polyester resin particle dispersion (1): 160 parts-White pigment particle dispersion (1): 75 parts-Release release agent particle dispersion (1): 20 parts-Ion exchange water: 220 parts-Anionic surfactant (TaycaPower, manufactured by Tayca): 5 copies

The above material was placed in a round stainless steel flask, 0.1 N nitric acid was added to adjust the pH to 3.5, and then 30 parts of a nitric acid aqueous solution having a polyaluminum chloride concentration of 10% was added. Then, after dispersing at a liquid temperature of 30 ° C. using a homogenizer (Ultratalax T50 manufactured by IKA), the mixture is heated to 45 ° C. in a heating oil bath at a rate of 1 ° C. per 30 minutes and heated at 45 ° C. It was held for 30 minutes. After that, 25 parts of the polyester resin particle dispersion (1) was added and held for 1 hour, a 0.1N sodium hydroxide aqueous solution was added to adjust the pH to 8.5, and then the mixture was heated to 84 ° C. for 2.5 hours. Retained. Then, the toner particles (1) were obtained by cooling to 20 ° C. at a rate of 20 ° C./min, filtering, thoroughly washing with ion-exchanged water, and drying. The volume average particle size of the toner particles (1) was 8.1 μm.

Two parts of titanium oxide particles (JMT-150FI manufactured by TAYCA Corporation) were added to 100 parts of the toner particles, and the mixture was mixed with a Henschel mixer at a stirring peripheral speed of 30 m / sec for 15 minutes. Then, the external toner was obtained by sieving using a vibrating sieve having an opening of 45 μm.
When the external toner was observed with a scanning electron microscope (SEM), the external additive had a spindle shape, and the major axis / minor axis value obtained by the above-mentioned measuring method was 4.5.

10 parts of the external toner and 100 parts of the carrier were placed in a V-blender and stirred for 20 minutes. Then, the white developer was obtained by sieving with a sieve having a mesh size of 212 μm.

[Examples 2 to 8]
The white toner and the white developer of each example were prepared in the same manner as in Example 1 except that the type of the white pigment particle dispersion was changed as shown in Table 1.

[Example 9]
A white toner and a white developer were produced in the same manner as in Example 1 except that the rate of temperature rise after dispersion at a liquid temperature of 30 ° C. was changed to a rate of 1 ° C. every 5 minutes.

[Example 10]
A white toner and a white developer were produced in the same manner as in Example 1 except that the addition amount of the polyester resin particle dispersion liquid (1) after holding at 45 ° C. was changed to 60 parts.

[Example 11]
A white toner and a white developer were produced in the same manner as in Example 1 except that the addition amount of the polyester resin particle dispersion liquid (1) after holding at 45 ° C. was changed to 10 parts.

[Example 12]
A white toner and a white developer were prepared in the same manner as in Example 1 except that the amount of the anionic surfactant was changed to 10 parts.

[Example 13]
A white toner and a white developer were prepared in the same manner as in Example 1 except that the amount of the anionic surfactant was changed to one part.

[Example 14]
The same as in Example 1 except that the polyester resin particle dispersion (1) was changed to a dispersion (solid content 20%) of styrene / acrylic resin (styrene / methyl methacrylate copolymer, copolymer ratio 15/85). To prepare a white toner and a white developer.

[Comparative Examples 1 and 2]
The white toner and the white developer of Comparative Examples 1 and 2 were produced in the same manner as in Example 1 except that the type of the white pigment particle dispersion was changed as shown in Table 1.

<Performance evaluation of white toner>
[Whiteness of white image]
Using the white toner of the example or the comparative example, a white image (concentration 100%, toner loading amount 9 g / m) is placed on an OHP film (Transparency OHP film for PPC laser, manufactured by Fuji Xerox, dimensions 21.0 cm × 29.7 cm). ^2. Dimensions 20.0 cm x 28.7 cm) were formed.
The image-forming material was repeatedly wound and unwound 100 times with a take-up tester (desktop endurance tester DLDMLH-FR, diameter 50 mm, manufactured by Yuasa System Co., Ltd.).
Before and after the winding process, the image forming object was wound around a transparent cylinder having a diameter of 100 mm so that the white image side was on the cylinder side, and the brightness was measured by a spectrophotometer. ^{Specifically, the L *} value (brightness) of the white image portion was measured from the OHP film side under a D50 light source using a spectrophotometer (X-Rite Ci62, manufactured by X-Rite). The measured L ^* values were classified into A to E as follows. Table 1 shows ^{the classification and L *} value before and after the winding process.

A: L ^* value is 75 or more.
B: L ^* value is 72 or more and less than 75.
C: L ^* value is 69 or more and less than 72.
D: L ^* value is 65 or more and less than 69.
E: L ^* value is less than 65.

[Color reproducibility of colored images]
A blue image (density 100%, toner loading amount 4 g / m ² ) was formed on paper (OS coated paper, basis weight 127 g / m ^{2, manufactured by Fuji Xerox) using cyan toner.} Using a spectrophotometer (X-Rite Ci62, manufactured by X-Rite), the L ^* , a ^* , and b ^* values of a blue image are measured under a D50 light source, and these are used for color reproducibility evaluation. It was used as a reference value.

Using the cyan toner used above and the white toner of the example or comparative example, a blue image (OHP film for PPC laser, manufactured by Fuji Xerox, dimensions 21.0 cm × 29.7 cm) is used. A laminated image (dimensions 20.0 cm × 28.7 cm) was formed by laminating a white image (density 100%, toner loading amount 9 g / m ² ) and a white image (density 100%, toner loading amount 9 g / m ^2). For the laminated image, the blue image was used as the lower layer (OHP film side).

The image-forming material was repeatedly wound and unwound 100 times with a take-up tester (desktop endurance tester DLDMLH-FR, diameter 50 mm, manufactured by Yuasa System Co., Ltd.).
Before and after the winding process, the image forming object was wound around a transparent cylinder having a diameter of 100 mm so that the white image side was on the cylinder side, and the color was measured by a spectrophotometer. Specifically, using a spectrophotometer (X-Rite Ci62, manufactured by X-Rite), the L ^* value, a ^* value, and b ^* value of the blue image portion from the OHP film side under the D50 light source. Was measured. The color difference ΔE was calculated based on the following formula and classified into A to E as follows. Table 1 shows the classification and color difference ΔE before and after the winding process.

式中、Ｌ_１、ａ_１、ｂ_１は、紙に形成した青色画像のＬ^＊値、ａ^＊値、ｂ^＊値であり、Ｌ_２、ａ_２、ｂ_２は、ＯＨＰフィルムに形成した青色画像のＬ^＊値、ａ^＊値、ｂ^＊値である。

In the formula, L ₁ , a ₁ , and b ₁ ^{are the L *} , a ^* , and b ^* values of the blue image formed on the paper, and L ₂ , a ₂ , and b ₂ are the blue formed on the OHP film. The L ^* value, a ^* value, and b ^* value of the image.

A: The color difference ΔE value is less than 1.5.
B: The color difference ΔE value is 1.5 or more and less than 3.0.
C: The color difference ΔE value is 3.0 or more and less than 5.0.
D: The color difference ΔE value is 5.0 or more and less than 8.0.
E: The color difference ΔE value is 8.0 or more.

1Y, 1M, 1C, 1K, 1W Photoreceptor (example of image holder)
2Y, 2M, 2C, 2K, 2W Charging roll (an example of charging means)
3Y, 3M, 3C, 3K, 3W exposure equipment (an example of static charge image forming means)
4Y, 4M, 4C, 4K, 4W developing device (an example of developing means)
5Y, 5M, 5C, 5K, 5W primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K, 6W Photoreceptor cleaning device (an example of cleaning means)
8Y, 8M, 8C, 8K, 8W Toner Cartridge 10Y, 10M, 10C, 10K, 10W Image Forming Unit 20 Intermediate Transfer Belt (Example of Intermediate Transfer)
21 Intermediate transfer element cleaning device 22 Drive roll 23 Support roll 24 Opposing roll 26 Secondary transfer roll (an example of secondary transfer means)
28 Fixing device (an example of fixing means)
P resin sheet (an example of recording medium)

107 Photoreceptor (an example of image holder)
108 Charging roll (an example of charging means)
109 Exposure device (an example of static charge image forming means)
111 Developing equipment (an example of developing means)
112 Transfer device (an example of transfer means)
113 Photoreceptor cleaning device (an example of cleaning means)
115 Fixing device (an example of fixing means)
116 Mounting rail 117 Housing 118 Opening for exposure 200 Process cartridge 300 Resin sheet (example of recording medium)

Claims (10)

Contains white toner particles containing a binder resin and a white pigment,
The BET specific surface area of the white pigment is 6.5 m ² / g or more and 8.5 m ² / g or less.
In the circularity distribution of the white pigment obtained by observing the cross section of the white toner particles, the circularity having a cumulative 10% from the smaller side is C10, and the circularity having a cumulative 50% is C50. And a white toner for static charge image development that satisfies the formula (2).
Equation (1): 0.900 ≤ C50 ≤ 1.000
Equation (2): 1.00 ≤ C50 / C10 ≤ 1.13 The white toner for static charge image development according to claim 1, wherein the C50 / C10 satisfies the following formula (2').
Equation (2'): 1.00 <C50 / C10≤1.08 In the cross-sectional observation of the white toner particles, when the Voronoi division is performed with the center of gravity of the white pigment as the base point, the average value of the areas of the Voronoi polygon is Sa (μm ² ), and the standard deviation is Ssd (μm ² ). The white toner for static charge image development according to claim 1 or 2, which satisfies the following formulas (3) and (4).
Equation (3): 0.150 ≤ Sa ≤ 0.350
Equation (4): SSD ≤ 0.250 The white toner for developing an electrostatic charge image according to claim 3, wherein the Sa satisfies the following formula (3').
Equation (3'): 0.180 ≤ Sa ≤ 0.300 The white toner for static charge image development according to any one of claims 1 to 4, wherein the white pigment has an average diameter of 150 nm or more and 400 nm or less, which is obtained by observing a cross section of the white toner particles. A static charge image developer containing the white toner for static charge image development according to any one of claims 1 to 5. The white toner for developing an electrostatic charge image according to any one of claims 1 to 5 is accommodated.
A toner cartridge that is attached to and detached from the image forming device. A developing means for accommodating the electrostatic charge image developer according to claim 6 and developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer is provided.
A process cartridge that is attached to and detached from the image forming device. Image holder and
A charging means for charging the surface of the image holder, and
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image holder, and
A developing means for accommodating the electrostatic charge image developer according to claim 6 and developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer.
A transfer means for transferring a toner image formed on the surface of the image holder to the surface of a recording medium,
A fixing means for fixing the toner image transferred to the surface of the recording medium, and
An image forming apparatus. The charging process that charges the surface of the image holder,
A static charge image forming step of forming a static charge image on the surface of the charged image holder, and
A developing step of developing an electrostatic charge image formed on the surface of the image holder as a toner image by using the electrostatic charge image developer according to claim 6.
A transfer step of transferring a toner image formed on the surface of the image holder to the surface of a recording medium,
A fixing step of fixing the toner image transferred to the surface of the recording medium, and
Image forming method having.

Images